/* * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) * Licensed under the GPL */ #include "linux/mm.h" #include "linux/sched.h" #include "asm/pgalloc.h" #include "asm/pgtable.h" #include "os.h" #include "skas.h" extern int __syscall_stub_start; static int init_stub_pte(struct mm_struct *mm, unsigned long proc, unsigned long kernel) { pgd_t *pgd; pud_t *pud; pmd_t *pmd; pte_t *pte; pgd = pgd_offset(mm, proc); pud = pud_alloc(mm, pgd, proc); if (!pud) goto out; pmd = pmd_alloc(mm, pud, proc); if (!pmd) goto out_pmd; pte = pte_alloc_map(mm, pmd, proc); if (!pte) goto out_pte; /* * There's an interaction between the skas0 stub pages, stack * randomization, and the BUG at the end of exit_mmap. exit_mmap * checks that the number of page tables freed is the same as had * been allocated. If the stack is on the last page table page, * then the stack pte page will be freed, and if not, it won't. To * avoid having to know where the stack is, or if the process mapped * something at the top of its address space for some other reason, * we set TASK_SIZE to end at the start of the last page table. * This keeps exit_mmap off the last page, but introduces a leak * of that page. So, we hang onto it here and free it in * destroy_context_skas. */ mm->context.skas.last_page_table = pmd_page_vaddr(*pmd); #ifdef CONFIG_3_LEVEL_PGTABLES mm->context.skas.last_pmd = (unsigned long) __va(pud_val(*pud)); #endif *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT)); *pte = pte_mkread(*pte); return 0; out_pmd: pud_free(pud); out_pte: pmd_free(pmd); out: return -ENOMEM; } int init_new_context(struct task_struct *task, struct mm_struct *mm) { struct mmu_context_skas *from_mm = NULL; struct mmu_context_skas *to_mm = &mm->context.skas; unsigned long stack = 0; int ret = -ENOMEM; if (skas_needs_stub) { stack = get_zeroed_page(GFP_KERNEL); if (stack == 0) goto out; /* * This zeros the entry that pgd_alloc didn't, needed since * we are about to reinitialize it, and want mm.nr_ptes to * be accurate. */ mm->pgd[USER_PTRS_PER_PGD] = __pgd(0); ret = init_stub_pte(mm, CONFIG_STUB_CODE, (unsigned long) &__syscall_stub_start); if (ret) goto out_free; ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack); if (ret) goto out_free; mm->nr_ptes--; } to_mm->id.stack = stack; if (current->mm != NULL && current->mm != &init_mm) from_mm = ¤t->mm->context.skas; if (proc_mm) { ret = new_mm(stack); if (ret < 0) { printk(KERN_ERR "init_new_context_skas - " "new_mm failed, errno = %d\n", ret); goto out_free; } to_mm->id.u.mm_fd = ret; } else { if (from_mm) to_mm->id.u.pid = copy_context_skas0(stack, from_mm->id.u.pid); else to_mm->id.u.pid = start_userspace(stack); } ret = init_new_ldt(to_mm, from_mm); if (ret < 0) { printk(KERN_ERR "init_new_context_skas - init_ldt" " failed, errno = %d\n", ret); goto out_free; } return 0; out_free: if (to_mm->id.stack != 0) free_page(to_mm->id.stack); out: return ret; } void destroy_context(struct mm_struct *mm) { struct mmu_context_skas *mmu = &mm->context.skas; if (proc_mm) os_close_file(mmu->id.u.mm_fd); else os_kill_ptraced_process(mmu->id.u.pid, 1); if (!proc_mm || !ptrace_faultinfo) { free_page(mmu->id.stack); pte_lock_deinit(virt_to_page(mmu->last_page_table)); pte_free_kernel((pte_t *) mmu->last_page_table); dec_zone_page_state(virt_to_page(mmu->last_page_table), NR_PAGETABLE); #ifdef CONFIG_3_LEVEL_PGTABLES pmd_free((pmd_t *) mmu->last_pmd); #endif } }